JPH09137300A - Method and apparatus for manufacturing belt sheet product consisting of stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the removing efficiency by executing the removal of continuous scale of Al-Si 300 and 400 stainless steel hot rolled band plates by multicell electrolytic pickling of an alkali electrolyte.

SOLUTION: As for the removal of scale, a band plate is subjected to scale breaker and blasting treatment according to necessary, and, after that, by plural electrolytic cells having a pair of electrodes in which anodes A and cathodes K are alternatively connected in the running direction of the band plate, at least one or more electrolytic cells provided directly after that and having only two pieces of anode electrodes A and an electrolytic cell with only one cathode electrode K connected via one of the anode electrodes A of the above electrolytic cells and a rectifier G1, primary pickling is executed. Next, with intermediate treatment of surface grinding and polishing interposed, again, by using ≥2 electrolytic cells with one cathode electrode K connected via the anode electrode A of the primary pickling cell and rectifiers G2 and 3, secondary pickling is executed. As the electrolyte, Na₂So₄ is used, and, at the time of the secondary pickling, about 0.3mol of H₂SO₃ is added according to necessary.

COPYRIGHT: (C)1997,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale removing equipment comprising a scale breaker, a blasting device, an abrasive surface cleaning device such as a brush, an electrolytic pickling bath, a washing machine, a reprocessing device and, in some cases, a subsequent processing device. In stainless steel,
In particular, steel grade AISI 300, 4 which contains a large amount of chromium alloy components
No. 00 stainless steel, annealed hot-rolled strips, and non-annealed hot-rolled strips.

[0002]

2. Description of the Related Art In the case of producing a product made of stainless steel, especially a strip plate product of steel grades AISI 300 and 400 containing a large amount of chromium alloy components, it is necessary to use a thermo-technical technique of the product in terms of forming and forming a crystal structure. Processing plays a decisive role. In these heat treatments, which reach temperatures of over 1200 ° C. in individual production stages, it is not possible to work in an oxygen-free atmosphere due to production and process constraints, and thus an oxidation process, also called a scaling process, is inevitable. .

The oxide film formed on the surface during this scaling process is extremely undesirable and disturbs not only during the subsequent production process, especially during the rolling process for forming, but also a trace amount of scale is present on the surface of the steel strip. Such oxide coatings must be repeatedly removed in the course of production, as the rest alone makes it impossible to achieve the desired surface quality of the steel in the production process.

[0004] When producing specialty steel products, the removal of scale layers from stainless steel is a special requirement for the technology to be applied and the associated process control, given that their surfaces are corrosion resistant. To raise.

Corrosion resistance means that the mass transfer with the surrounding phase, generally air, produces a corresponding reaction product, eg, "rust", through the surface of the stainless steel.
This means that it can only go very slowly.

Stainless steel forms a so-called passivation film in oxidizing acids, of course under normal atmospheric conditions, ie in air, which is characterized by having very few lattice defects. Due to the small number of lattice defects, the diffusion process (mass transfer via ion transport) can only proceed very slowly and thus very slow film growth can occur.

The passivation film of stainless steel, which is extremely efficient in terms of corrosion behavior, contains oxide films, hydroxides, and trace amounts of iron elements, which are only a few atomic layers (1 to 20 nm) thick in various mixed crystal shapes. It is mainly composed of a chemically very stable oxygen compound of the alloying element chromium (Cr ₂ O ₃ ) characteristic of the steel in question. The elemental chromium in steel alloys plays a special role in the individual scaling processes during the production process, and thus also in the scale layer removal technique, as will be explained in more detail later.

In addition to the corrosion resistance and mechanical properties of specialty steels, the surface quality of specialty steel products--the technically expressed roughness thereof--plays a major role for the range of application of such products. Corrosion resistance and surface quality, along with pure material parameters, are the most important characteristic properties of specialty steel products.

The strip product made of stainless steel is subjected to a rolling operation in the course of its production, where the strip is rolled to lengthen, forcibly reducing the plate thickness, and thus also the area.

Two rolling operations are distinguished, a hot rolling operation and a cold rolling operation: When the material, eg slab, is heated to a temperature of about 1250 ° C. for the rolling operation, the resulting product is hot. It is called a rolled strip. However, when the steel strip is subjected to a rolling operation at room temperature, this product is called a cold rolled strip.

As can be easily envisioned, generally hot rolled strips are processed with relatively large sheet thicknesses and cold rolled strips are naturally processed with relatively small sheet thicknesses. The thickness ranges of the individual production lines may more or less overlap.

Preferably, in one continuous course, starting from a so-called slab as a steelmaking product, firstly in several hot rolling passes, and finally after a certain plate thickness, the final cold rolling is carried out. In the pass, cold-rolled strips with the desired strip thickness and surface quality are produced.

The thermal conditions during the forming hot rolling pass not only lead to the formation of a well-defined scale layer on the steel surface under the prevailing conditions, but also to the undesirable crystal structure of the steel matrix. And an organizational structure.

In the case of hot rolled strip, heat treatment (annealing)
Austenitic stainless steel (steel type AIS
A completely recrystallized structure is obtained by the transformation from I300).

Due to the high alloy content, the recrystallization is strongly delayed and the hot rolling strip is only able to undergo a partial recrystallization in the coil during the rolling operation and during subsequent cooling. In the center, there is an agglomerate that extends long, without recrystallization, partly over the entire cross section. Steel type A
In the ISI 400 ferritic stainless steel, a martensite structure (= precipitation of dissolved carbon as spherical carbide and reduction of high dislocation density) produced during cooling after rolling by annealing operation along with recrystallization. The spheroidizing annealing of must be achieved.

Spheroidized annealing is not required for stabilized ferritic steels of, for example, AISI 409, 439 (carbon is stably bonded as titanium carbide TiC) which has a ferritic structure in the rolled state.

A material temperature of 800-900 ° C. for ferrite and 1200 ° C. for austenite when achieving a continuous ferrite or austenite microstructure in this annealing operation, which is essential for producing the desired crystal and microstructure of the steel. Material temperatures up to and including must be achieved, and this annealing operation also scales the steel surface. The quality and quantity of oxide formation can also be adjusted within limits by appropriate process control. This point will be mentioned later.

The scale formed on the steel surface during hot rolling is referred to as the rolling scale, and, correspondingly, the scale formed on the steel surface during the annealing operation is referred to as the annealing scale. The two types of scales are characteristically different, and this difference originates in the initial condition and the boundary condition when the scale is generated. This point will be described in more detail below.

Steel strips, especially steel grade AI containing a large amount of chromium component
With the scaling process during the production of SI 300, 400 stainless steel, on the one hand the strip, on the one hand, and thus of course also the strip surface, in order to prepare it for subsequent rolling operations, In order to get the expected state in terms of quality,
Simultaneously and inevitably, the problem of repeatedly and completely removing the scale layer in subsequent subsequent steps occurs.

Although the scale formation on the surface of chromium-rich stainless steels is certainly complex and depends on a series of different parameters and conditions, the basis of this scale formation is basically the following: There is a mechanism:

When iron is exposed to an oxidizing atmosphere, various oxide films, wustite (FeO), magnetite (Fe) are produced depending on the temperature range and oxygen pressure.
₃ O ₄ ) and / or hematite (Fe ₂ O ₃ ) are produced. It is possible to predict what kind of oxide is stable in equilibrium with the gas phase and what kind of film series of oxidation products is based on thermodynamic law and data. The growth of the oxide film is, for the moment, determined by surface reactions and is linearly dependent on time. As the thickness of the oxide film increases, the diffusion process in the oxide determines the rate, and the parabolic law is valid. Diffusion in oxides is possible due to disordered substitution of ionic lattices, vacancies or intermediate lattice atoms.

Oxides with slight disordered substitutions that form a hermetic oxide film only grow slowly and can be good protective layers against hot corrosion. It is the alloying elements of chromium, aluminum and silicon that form the protective oxide film.

Special steel alloys having a chromium content of more than about 15.5% can be used in an atmosphere having a sufficient free oxygen content.
When annealed at a temperature of up to 00 ° C., a stable and continuous (Cr, Fe) ₂ O ₃ mixed oxide film spontaneously forms at the interface between the gas phase and the metal phase. This continuous coating is a diffusion barrier for oxygen in the vapor phase and elements of the steel alloy that largely prevents further oxidation of the underlying steel alloy elements. Simultaneously with the formation of this mixed oxide film on the surface of the metal base material, the metal base material becomes deficient in chromium to a deep portion.

The fact that the mixed oxide film is formed on the metal surface and the chromium of the underlying metal matrix is deficient at the same time is explained by the high affinity of chromium, which binds to oxygen and becomes a stable oxide. You can As can be read from the thermodynamic stability diagram, aluminum, silicon,
Manganese and chromium are already oxidized even when the oxygen pressure is very low, and therefore form an oxide film in an atmosphere of low oxygen content. The oxygen pressure required to form an oxide film on iron and nickel is as high as 10 orders of magnitude. The oxidation process --- provides a strong concentration gradient of the chromium component in the metal matrix over the interface with the oxide phase, which causes diffusion of chromium from the film deep in the metal matrix toward the interface. , And the oxidation reaction is triggered there.

The metal matrix, the interface that occurs between the individual phases,
Due to these processes, which are physically and chemically induced in the individual oxide phases and in the external atmosphere during heat treatment, the scale in which chromium is generated from the near surface film of the metal base material is stronger than that of other alloy components. It is transported in the direction of the layer, thus causing a decrease in the concentration of the alloying element chromium in the film near the surface of the metal base material below the mixed oxide film formed.

This effect is referred to as chromium deficiency, and the film in the vicinity of the surface of the metal base material on which this effect occurs is referred to as a chromium deficient region of the metal base material.

As long as the mixed oxide film is consistently flawless,
Further oxidation of the metal matrix can only proceed very slowly. However, if this protective film breaks down,
Oxidation of the underlying metal matrix proceeds very rapidly. The "therapeutic" mixed oxide film that recoats this area is
The chromium content of the underlying metal has a certain concentration--temperature 7
About 18.5% at 00 ℃; about 1 at 1000 ℃
It can be generated only when it does not fall below 5.5%-.

If it is not possible to produce these "therapeutic" mixed oxide coatings at the fracture site, oxidation will occur in the course of other processes to produce the (Fe, Cr) ₃ O ₄ spinel structure. This spinel structure is a diffusion barrier that is inferior to the mixed oxide film. When the other conditions are the same, the oxidation rate increases by several decades when Cr is 16% to 8%.

At the beginning of the high-temperature oxidation of the material in question here, on the basis of insufficient free oxygen content in the tempering atmosphere or on the basis of an excessively low chromium content in the alloy, If it is not possible to form a stable continuous mixed oxide film having the property of protecting from the oxidation of, the (Fe, Cr) ₃ O ₄ spinel layer is formed on the metal surface for the time being. Fe ions diffuse and permeate the spinel layer relatively quickly and are then oxidized at the oxide-gas interface to iron oxide, wustite FeO, magnetite Fe ₃ O ₄ and / or hematite Fe ₂ O ₃ .

The scale layer thus produced is composed of two layers--
-The inner layer is made of Fe-Cr oxide, and the outer layer is made of Fe oxide-. The formation of this remarkable double structure can be explained by the fact that the mobility of Fe is much larger than that of Cr in the Fe and Cr oxide films. Therefore, unlike Fe, a very small amount of Cr has a predetermined amount. Under these conditions, the Fe and Cr oxide films can pass through, and thus almost pure Fe oxide will be formed in the outer scale layer.

The relative motility of the individual metals that make up the alloy in the spinel layer can be expressed in the following order: Mn ²⁺ > Fe ²⁺ > Co ²⁺ +> Ni ²⁺ > Cr ²⁺ Under normal conditions, the oxidation of the metal is consistently uninterrupted by the protective coating.

On the basis of the annealing conditions, in particular the partial pressure of free oxygen in the annealing atmosphere and the presence of a sufficient chromium component in the metal alloy, it protects the metal matrix from further oxidation (Cr, When the Fe) ₂ O ₃ layer is formed, the scale thickness is around 1.0 μm. Under these conditions, the scale thickness only slightly depends on the annealing time. The scale consists essentially of mixed oxide (Cr, Fe) ₂ O ₃ .

If this mixed oxide film cannot be produced, or if it is destroyed, the underlying material will be further oxidized.

The formation of a "therapeutic" mixed oxide film which also protects against further oxidation when sufficient chromium components are present in this material to form a mixed oxide under the given conditions. become. In this case, the scale thickness is several μm
It depends on the degree of disability. The scale again consists mostly of mixed oxides (Cr, Fe) ₂ O ₃ .

Producing the mixed oxide film when the chromium component is not present in the metal alloy or under annealing conditions--too low free oxygen partial pressure in the annealing atmosphere. If this is not possible, the oxidation of the metal will continue consistently. In this case, substantially (Fe, Cr) ₃ O ₄
A spinel structure forms, followed by a very thick iron oxide layer. In this case, the scale thickness is a function of the annealing time and may be several 10 ¹ μm to 10 ³ μm.

A slab made of stainless steel is used in a pusher type or walking beam type heating furnace for about 1200-12.
When heated to a temperature of 50 ° C., a stable continuous mixed oxide film cannot be formed under these conditions. Rather, a (Fe, Cr) ₃ O ₄ spinel layer is formed at the phase boundary with the metal, and a surface layer made of iron oxide is formed thereon.

This oxide film (scale) has a thickness of several millimeters. This scale layer is 100-2 in a scale washer before entering the first roll stand.
It is removed by spraying with high pressure water of 00 bar. The scale remaining on the slab will be pressed onto the material surface during rolling, leaving so-called scale defects. As a result, finished products will be excluded. However, during hot rolling, new scales are continuously generated, which undergo various cracks due to mechanical stress during the rolling operation, which repeats before and between the stands of wide hot strip rolling mills. It is removed by spraying with high pressure water. From the final stand of the finishing mill, the strip moves out at a temperature of 900 to 1000 ° C. The strip surface is covered with an extremely thin oxide film (<1 mym).

When subsequently cooling the strips in reels and as winding coils in the cooling zone, the scale layers are
Grow to a thickness of 10 μm. The scale is composed of (Fe, Cr) ₃ O ₄ spinel at the phase boundary with the metal and the iron oxide surface layer. Above 560 ° C, iron oxide is mainly wustite F
It consists of eO. At relatively low temperatures, wustite decomposes into magnetite Fe ₃ O ₄ and iron particles embedded therein. Furthermore, hematite Fe ₂ O, mainly on the edges of the strip, and on the outer and inner walls of the coil under strongly oxidizing conditions.
₃ Surface layer may be generated. The scale cracks during cooling.

The thickness of the chromium-deficient region on the surface of the strip is << 1 μ
m, and the Cr enriched scale layer has a thickness of about 2 μm. The thickness of the Cr-enriched scale layer and the thickness of the Cr-deficient layer on the metal surface decrease as the reel temperature decreases.

The surface covered with such a hot rolling scale is annealed for a long time in a bell-shaped annealing furnace (> 20 h).
When exposed to a diffusion process, the diffusion process leads to an increase in the Cr-enriched spinel layer at the phase boundary with the metal and a significant depletion of Cr at the metal surface. The spinel layer has a thickness of about 3 μm and its Cr content is considerably higher than before the annealing process. The Cr-deficient region may be up to 5 μm wide. All scale layers have a thickness of 10 to 15 μm. There is often a thin iron layer (reduced iron oxide) on the oxide film.

When the hot-rolled strip is annealed in the continuous furnace of the annealing / pickling line with an annealing time of several minutes and a controllable oxygen partial pressure, the total scale layer thickness is reduced. After all 10
Rise to ~ 15 μm. However, Cr deficiency can occur only in a small range because the annealing time is short, the Cr deficiency region has a thickness of about 2 μm, and the Cr concentration in the oxide film at the phase boundary with the base metal is also small. . An additional note regarding the removal of such annealed scale layers on hot rolled strips is that the annealed scale layers are provided with a continuous mixed oxide film as in the case of properly annealed cold rolled strips. Absent. Therefore, these scale layers are also a factor 10 thicker than the comparable scale layers on the cold rolled strip.

The scale surface of the hot-rolled strip thus annealed shows a high proportion of iron oxide and embedded Cr-rich oxide. A local battery, which is indispensable for chemical pickling, can be produced together with a scale layer by electrolytic coupling with a chromium-deficient region or a base metal, and a mechanism for sneaking under the oxide thin film that appears in parallel and scattering it The mixed oxide film at this area ratio of iron oxide is chemically extremely stable when the chromium-deficient region or a suitable potential for rapidly dissolving the base material in the acid can be generated by It is permeable to detergents (but the oxides dissolve very slowly in the acid or acid mixture) and removes the scale film by acid at pickling rates that are economically interesting. However, the generation of the local battery occurs only very slowly, and in such a hot-rolled strip scale, an economical pickling rate in acid cannot be achieved.

Therefore, preferably such a scale layer on such a surface is such that a portion thereof is exposed so that a chromium-deficient layer, or sufficient free surface of the matrix, is exposed to achieve an economical pickling rate. It is removed by a physical operation such as blasting and / or brushing.

In most cases, not only the critical area ratio of the chromium-depleted layer or the base material but also a very large area ratio is exposed in the mechanical scale removal operation after annealing of the hot-rolled strip ---- and chromium depletion is also caused. The layer is not as prominent as in the case of cold-rolled strips and therefore the thickness of this layer is not too large ---- if the concentrations of the individual components in the mixed acid are chosen appropriately, high pickling. It can be pickled at a rate.

Annealing of the hot-rolled strip is carried out in order to recrystallize the metal structure after hot-rolling and cooling. This is in agreement with the decrease in the increase in strength value caused by hot rolling and cooling. However, steel grade AISI 300
The strength increase is only 10 to 20% in the case of 80% of the material of steel type and AISI 400. These materials could be cold worked (50-80%) without an annealing operation. However, the remaining 2 materials of steel grade AISI 400
0% must be annealed before cold working.

In order to comply with the above technical conditions, the individual treatment steps have hitherto been carried out with the following equipment configurations: hot-rolled strip treatment of all materials-annealing, -blasting, -oxidizing acids. Internal pickling, often electrolytic pickling (but the efficiency at material blasting is only 20-30%). Then, cold working is performed in a reversible rolling mill up to 13 passes in order to produce a cold rolled strip with the desired finished thickness.

When a hot rolled strip is manufactured as a final product, a strip having a roughness of 4 to 6 Raμm is produced with this equipment configuration.

The treatment of the cold-rolled strips is carried out in one or two runs in a cold-rolled strip annealing / pickling line with the following treatment stages, depending on the material quality and the degree of processing: -Annealing, -electrolytic pickling, -pickling in oxidizing acids.

To summarize this practice applied conventionally,
The following significant drawbacks arise with respect to the following material-specific economic and ecological parameters: 1. The hot rolled strip as the final pickled product is 4-6Raμ.
It is produced with a surface roughness of m. 2. Cold-rolled strips are made in three independent steps: -annealing and pickling of hot-rolled strips-cold working-annealing and pickling of cold-rolled strips. This is high energy cost, labor cost,
Coupled with transportation costs and high environmental impact.

In order to partially avoid the above-mentioned drawbacks, a method has already been developed which enables the operation sequence from the hot-rolled strip to the finish cold-rolled strip in one line. The following steps are provided in one production line there. That is: -mechanical scale removal of hot-rolled strips (without or with annealing),-cold rolling in 2-5 stands, -annealing, -pickling.

As a drawback of this construction, 100% removal of scale is not possible by mechanical scale removal, and still pickled hot rolled strips with high surface roughness values are produced. In order to be able to produce a perfect surface in the subsequent step, cold rolling, 100% removal of scale is required for optimum surface quality of the cold rolled strip, which is the heaviest The conditions cannot be observed.

[0052]

The object of the present invention is to start from the problems and drawbacks of the prior art, and to pickle the stainless steel hot rolled strip (stainless steel grade AISI 300, 400 in one line in an economical manner. ) --- even with material qualities such as ferrite 430, which must be annealed as hot-rolled strips before other treatment --- slightly 1-2 .mu.
Manufactured with surface roughness of mRa, 100% scale removal in one run, thickness reduction of 50-80% depending on rolling operation, allowing annealing, descaling and finishing. It is to provide a method and equipment. at the same time,
In order to ensure that the reflectance is significantly reduced by a good darkening of the surface, it must be ensured that the strip without 100% scale has a passivation film before cold working.

[0053]

In order to solve this problem, the two methods described by the features of claims 1 and 4 are the hot rolling strips which are annealed or the hot strips which are not annealed, respectively. Suggested for rolling strips.

The installation for carrying out the method according to the invention is protected by claim 7. According to the present invention, without increasing the surface roughness of the strip, or while reducing the surface roughness of the strip by the required scale removing operation to increase the surface roughness, heat treatment before cold working is performed. Succeeded in ensuring 100% scale removal of the hot rolled strip.

This point is particularly important for the quality of the material, for example ferrite 430, which must be annealed as a hot-rolled strip before other treatments. As mentioned at the beginning, the scale generated at that time cannot be economically removed by the pickling technique. In order to remove the scale, a mechanical device such as a blasting device, a brush, an abrasive powder, etc. must expose the chromium-depleted layer or a sufficient free surface of the base material.

To date, blasting of the strip surface has proved to be the most efficient and most economical solution for this application case. However, this has a surface roughness of 6 μmRa.
It is associated with the drawback of rising to. The method and the installation according to the invention also have the technical possibility to carry out the reduction of the surface roughness to 1.0-2 μm Ra using a grinding brush also for these materials.

Another advantage of the method and descaling equipment according to the invention is the reflectance of the descaling strip. Cold-rolled stainless steel strip has high reflectance as is known,
This high reflectivity requires relatively high equipment and energy costs for subsequent annealing. For this reason, it is advantageous for economic reasons to design the descaling equipment so that the strip is 100% descaled before cold working, but with a passive film. This passivation film should have a maximum film thickness of 100 nanometers to avoid surface defects during cold rolling, but should also ensure a good darkening of the surface to significantly reduce the reflectance. Will.

The present invention takes into account all of these material-specific economic aspects, and the present invention is envisioned as a multi-functional technology unit, which enables: 1. 100% scale removal of both hot-rolled strips of non-annealed and hot-rolled strips of all stainless steel grades AISI 300, 400. 2. 100% scale removal of hot-rolled strip that is not annealed without increasing surface roughness of the hot-rolled strip by blasting; 100% descaling of the strip with the possibility of lowering the surface roughness of the annealed hot-rolled strip, which was increased by the blasting device, by means of a grinding brush. 4. All strips can be provided with a passivation film that does not interfere with the subsequent rolling operation, provided that the surface of the hot-rolled strip stripped of any oxides is colored so that the reflectance of the strip is significantly reduced. To be done.

[0059]

According to the idea of the invention, this scale-removing facility consists of an electrolytic pickling machine of a completely new concept and a separate device known per se which is paired with it.

In order to enable or facilitate descaling for subsequent equipment in the case of any material, and to make good flat strips, this descaling equipment is equipped with scale breakers and stretch straighteners. Consisting of a device that works as.

In order to produce the exposed oxide surface required for the rapid generation of the required potential and the economical pickling for the hot-rolled strip to be annealed, a blasting device (depending on the strip speed) 1
~ N devices) are provided in the subsequent stage. The subsequent electrolytic pickling machine, in the electrolytic bath according to the known electrolytic pickling system,
In the new concept, the current flow is controlled by the anode length 1 /
3, the cathode length is provided to operate by connecting to 2/3. The number (n) of electrolysis cells is adapted to the strip plate passing speed.
An electrolytic cell including more than two anodes as a power feeding unit is installed in a subsequent stage of these electrolytic cells. The subsequent electrolyzer only contains one cathode. This cathode is connected via a rectifier to one of the anodes of the anode electrolyzer.

In its operation, the high-pressure liquid injection device or brush device used in the latter stage of the anode-connected electrolytic cell has the following features. In the case of a hot-rolled strip which is not annealed, the dissolved scale oxidized by the electrolytic pickling section is removed, or In the case of annealed hot-rolled strips, it additionally reduces the high strip surface roughness produced by blasting.

However, experiments have shown that in the above-mentioned technique the strip is still descaled as desired for cold working or optimum surface quality of the annealed pickling hot rolled strip. Absent. To that end, another retreatment is required after the abrasive surface cleaning. According to the invention, two electrolytic cells of an electrolytic pickling machine with a cathode circuit perform the final cleaning (100% removal of residual scale).

The technical aspects of this arrangement and the method according to the invention are based on the following conditions: Under the anode the strip is cathodic and necessarily has a pH value of about 14 on the strip surface. This means that in this case only gas evolution is effective as a bursting factor for scale removal.
On the cathode side, however, the strip is anodic and a pH value of about 0 occurs on the strip surface. This corresponds to 1 molar concentration of H ₂ SO ₄ on the strip. Only this part of the electrolytic pickling machine
Descaling deep in the holes can also be guaranteed.

In the case of material parts which are treated as hot-rolled strips to be annealed, the entire electrolysis part may instead of or supplement Na ₂ SO ₄ as electrolyte in order to increase the gradient of the descaling effect. H ₂ SO containing about 3 molar concentration
Operated at ₄ .

The critical point here is that the use of 3 molar H ₂ SO ₄ removes the residual scale deeply and deepens the pores only in the electrolytic cell provided downstream of the polishing apparatus. To produce a passive film. This passive film has a film thickness of 50 to 100 nm. This passivation film is
It does not disturb the rolling operation with respect to the surface quality of the strip, but has a positive effect on the reflectivity for annealing.

The installation according to the invention is clarified by a single drawing.

[Brief description of the drawings]

1 shows an installation according to the invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michael Henches, Federal Republic of Germany, Day 45147 Essen, Becklinstraße 4 (72) Inventor Andreas Jenichen, Federal Republic of Germany, Day 40468 Düsseldorf, Dorrenweg 14 (72) ) Inventor Reiner Kilfe Germany, Day 40457 Düsseldorf, Schiffbahnweg 33 (72) Inventor Horst Edel Germany, Day 40595 Düsseldorf, Bad-Harzburger-Schutler 89 (72) Inventor Jürgen Frugge Germany, Day 47228 Duisburg, Grabenacker 108 Ar

Claims (10)

[Claims] 1. Stainless steel, especially chromium, in a scale removal facility comprising a scale breaker, a blasting device, an abrasive surface cleaning device such as a brush, an electrolytic pickling bath, a cleaning device, a reprocessing device and possibly a subsequent processing device. What is claimed is: 1. A method for continuously treating an unannealed hot-rolled strip consisting of stainless steels of AISI 300, 400, which is rich in alloy components, consisting of stainless steel, characterized by a combination of the following successive steps: Continuous processing method for hot-rolled strips without annealing. a) a step of breaking the scale of the hot-rolled strip that is not annealed by stretching and roll type straightening, b) electrolysis in an alkaline electrolyte that connects the anode and cathode alternately several times to polarize the strip A step of pickling, c) a plurality of anode connecting electrodes provided directly before and after, a corresponding cathode electrode of the strip, and subsequently an anode electrode of the strip produced by the cathode connecting electrode. A subsequent pickling step in the electrolyte or another electrolyte, d) a strip surface polishing step, e) in at least one alkaline electrolyte having a plurality of electrodes connected exclusively to the cathode and an anode of the strip Electrolytic pickling step performed again in step f) Reprocessing step such as cleaning, brushing, recleaning, and drying of the strip surface. 2. N as an electrolyte in steps b) and c)
A continuous process for hot-rolling unannealed stainless steel strip according to claim 1, characterized in that a ₂ SO ₄ is used. 3. Na ₂ S as the electrolyte in step e)
O ₄ is used, and / or the strip surface H ₂ SO ₄ in order to passivate, preferably 3 molar, characterized in that it is used, stainless steel according to claim 1, 2 A continuous treatment method for hot-rolled strips without annealing. 4. The method for continuously treating an unannealed hot-rolled strip made of stainless steel according to claim 1, wherein step d) is performed by high-pressure liquid jet. 5. The method for continuously treating an unannealed hot-rolled strip of stainless steel according to claim 4, characterized in that water or an electrolyte is used as the high-pressure liquid. 6. Stainless steel, especially chromium, in a scale removing facility comprising a scale breaker, a blasting device, an abrasive surface cleaning device such as a brush, an electrolytic pickling bath, a washing device, a reprocessing device and possibly a subsequent processing device. What is claimed is: 1. A method for continuously treating annealed hot rolled strips of steel grades AISI 300, 400 stainless steels rich in alloy constituents, characterized by a combination of the following successive steps, consisting of stainless steel: A method for continuously treating annealed hot rolled strips. a) A step of destroying the scale of the hot-rolled strip to be annealed by stretch and roll straightening, b) A step of blasting the strip surface once or several times, c) Alternately connecting anode and cathode Electrolytic pickling in an alkaline electrolyte having a plurality of electrodes, d) said electrolyte or other having a plurality of anode connecting electrodes placed directly before and after it, followed by one cathode connecting electrode A subsequent pickling step in the electrolyte, e) a grinding step of the strip surface, f) an electrolysis which is carried out again in at least one alkaline electrolyte having a plurality of electrodes connected exclusively to the cathode and an anode pole of the strip. Pickling process, g) Reprocessing process such as cleaning, brushing, re-cleaning and drying of strip surface. 7. H as an electrolyte in steps c) and d)
_The method for continuously treating annealed hot rolled strips of stainless steel according to claim 6, characterized in that ₂ SO ₄ is used. 8. Na ₂ S as an electrolyte in step f)
7. Stainless steel according to claim 6, characterized in that O ₄ is used and / or H ₂ SO ₄ is used for passivating the strip surface, preferably in a 3 molar concentration. A method for continuously treating annealed hot rolled strips. 9. Stainless steel, especially chromium alloy components, in a scale removing facility comprising a scale breaker, a blasting device, an abrading surface cleaning device, an electrolytic pickling bath, a cleaning device, a reprocessing device and possibly a subsequent processing device. An annealing hot-rolled strip made of stainless steel of AISI 300, 400, which contains a large amount of steel, and a facility for continuously processing an annealed hot-rolled strip, which are provided one after another in a facility for continuously processing An annealing hot-rolled strip made of stainless steel and a non-annealed hot-rolled strip continuous treatment facility characterized by having an equipment part. a) a stretch-roll type straightening machine as a scale breaker for the hot-rolled strip fed in, b) a blasting device or blasting devices for cleaning the strip surface, and c) an alkaline pickling bath or baths, 1/3 vs. 2 /
Electrolytic pickling machine with alternating anodes in 3 known anode / cathode lengths, n electrolyzers with electrodes connected to the cathodes, d) immediately followed by two or more exclusively anode electrodes An electrolytic cell directly connected to said electrolytic cell, comprising only at least one electrolytic cell having and one cathode electrode connected to one of the anode electrodes via a rectifier, e) selective strip surface A device for surface polishing or surface grinding, f) another electrolytic pickling bath with at least one alkaline electrolyte having at least two exclusively cathode-connecting electrodes connected to the anode electrode of the first pickling bath via a rectifier , G) Reprocessing equipment for strip surface cleaners, brushes, re-cleaners, strip dryers, etc. 10. An unannealed hot rolling of stainless steel according to claim 9, characterized in that the device for surface-polishing the strip surface is a high-pressure liquid jetting device for water or electrolytes. Continuous processing equipment for strips.